Leading figures from the fields of academia, business, arts and NGOs have also signed the letter, including Scotland’s former chief medical officer Sir Harry Burns, historians Sir Tom Devine and Chris Smout, and director of Friends of the Earth Scotland Dr Richard Dixon.

In the letter they write: “We see our society, economy and politics becoming ever more undermined due to the impact of Brexit. We recognise that a narrow majority voted to leave the European Union, but the disastrous consequences are now becoming ever clearer - every day. Even before the UK has left the EU, we face falling living standards, rising inflation, slowing growth and lower productivity.

Theresa May holding a cabinet meeting. Picture; PA

“Our international reputation has been seriously damaged, leaving the UK weak, with diminished influence, in an increasingly uncertain and unstable world.”

The letter continues: “In a democracy, it is always possible to think again and to choose a different direction. We need to think again about Brexit, to have a UK-wide debate about calling a halt to the process and changing our minds.”

It concludes: “We call for a national debate on Brexit. We ask our fellow citizens, and our politicians, to think again. It is time to call a halt to Brexit.”

He said: “Enough is enough because we see Brexit taking us towards a catastrophe - there are no perceived benefits - and in the meantime we see negotiations in Brussels going nowhere, we see a Cabinet and Government at Westminster shambolically handling affairs.

“And one of the big issues for me is that, over the next two years, Parliament in London will face seven Bills about exiting the European Union. What happens then to housing? What happens then to climate change? What happens to the big issues that Britain faces?

“They’ll be in the cupboard while we pursue this pointless distraction.”

The former first minister said it was “possible” that Parliament could overturn the Brexit vote, adding: “There will be a lot of opportunities over the next two years to derail and potentially reverse that decision.”

He said he hoped for a change in the Labour Party’s position following a general election he felt had demonstrated a shift in opinion.

“At the end of the day, I believe sincerely, as a passionate European, that this is a huge mistake, a national exercise in self-harm, a pointless distraction.

“I believe that view is shared by many of my colleagues but we now have to find a way of putting that into the public arena, having a much bigger, better debate, and as that happens I believe that the Tory Party will continue to be a shambles and of course these negotiations will go nowhere.

“This is about the future of Britain, this is a new battle for the future of Britain.”